Short wave radio transmitter



Jan. 31, 1939. C, w, MCE A 2,145,735

SHORT WAVE RADIO TRANSMITTER H15 Attorheg.

Jan. 31, 1939. L v; Wn RlcE" 2,145,735

SHORT WAVE RADIO TRANSMITTER Filed Jan. 29, vv193e; v 2 sheets-sheet 2 Ihvehtov: Chester Rice,

I by is Attorneu.

Patented Jan. 31, 1939 s PATENT OFFICE General Electric C New York f v ompany, a corporation o!k 'Application January 29, 193s-, serial No. 61,377

. e 27 Claims.

i My/invention relates to short Wave radio transinitters and `more particularly to those of the x electronic roscillator typein which the electron 'transit time governs thefperiod of oscillation.

` In order that my invention will be more readily understood, a brief discussion Aof the prior .n development in the artisnecessary. Barkhausen and Kurz discovered in 1919 that electronic oscil-A lationsare Vproduced in a triodeV whena positive l potential is applied'to theV grid and a small negative' potential is applied to the plate. The explanation .of these oscillations given `by kBarkv`hausen and Kurz is that :electrons'are accelerated fromv the cathode to the positive grid where, some offthe Aelectronsdue to their high Velocity, overshootthegrid and pass into the grid-plate region. 'In' thisregion they are retardedand turned back Hin the direction ofthe grid. 'Ihosje which pass the grid on their return tripand reach the neigh- 20 borhoodof .the cathode are retarded and [then once more acceleratedin the direction ofthe grid. "Q Laten work byZacek indicated that 'oscilla- .tions similarto those` of Barkhausen'` and Kurz `could ,be produced in'circuits using a Hull mag- `Lne'tron `ofthe concentric--ecylindrical diode type having amagnetieeldfin thedirection of the j electrode axis.V ln -.thel magnetron, the `electron f orbits are determinedlbythe combined effect/of the electrostatic and the electromagnetic vfields. .',Zacek foundwthat the wavelength for optimum oscillation strength ywas giVen `approximately by const.

wherev f `)cv/'ave length.

. 1H=magnetic eld intensity'.

It wasy also shown by Okabe that electronic oscillations maybe generated in cylindrical and split yanode magnetrons. e

'Ihe oscillations produced by the magnetron and bytheBarkhausen and Kurz oscillators were vfound to have certain characteristics in common. y

the above described (Cl. Z50-27.5)

ultra short wave radio transmitter having greatly improved power output characteristics and frequency stability.`

A further object of my invention is to provide an improved means for modulating oscillations. lA still further object of my invention is to provide an improved means for mounting and cooling electron discharge devices. e

The novel features which I believe to be characteristic of my invention are set forth with pari ticularity in thev appended claims. My invention itself, however, both as to its organization yand method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 is an elevation partly in cross section of one embodiment of my invention. Fig. 2 is an enlarged cross sectional View of a portion of the transmitter which includes the modulating coil and the flux control ring. Fig. 3 isan enlarged cross-sectional View of the magnetron of Fig. 1. Fig. 4 is a cross-sectional view of a tuning collar used in connection with V'the radiating member'of Fig. l. Fig.` 5 is an elevation partly in cross section of amodified ,form of my invention. Fig. 6 illustrates in greater detail my improved method of'oooling electron discharge devices. 'Fig. 7 is an elevation' partly y'in cross-section of'another embodiment of my v inventionk wherein electro-magnets are used to produce the necessary axial magnetic eld for magnetron operation.

Referring to Fig. 1 of the drawings, I have shown therein a transmitter embodying my invention, and which includes a permanent magnet l and an electron discharge device 2. Discharge device 2 ishoused almost entirely within axial apertures 3 and 4 of the two truncated conical pole pieces and 6 which are secured to the ends of permanent magnet I. The discharge device is preferably of cylindrical form having a cylindrical metal anode 1, the opposite ends of which are supported in the respective apertures 3 and 4 of the pole pieces. The apertures themselves have an irregular Vcontour as may be seen from the drawings. These irregular contours provide suitable shoulders for mounting electron discharge device 2 as will hereinafter be pointed out.

It will be notedfrom the drawings that the right end of anode 1 is provided with a ring or collar 8 withy closely ts against the inner surface of aperture 4 and which is held in position by the inner end of1 a split brass housing 9. Housing 9 is suitably form fitted within the aperture and is provided witha screw threaded follower 9' at the outer end which cooperates with corresponding threads in the pole piece whereby upon rotation of the follower 9 the inner end of the housing 9 is pressed firmly against the collar 3 which in turn engages a shoulder of aperture 4. If water cooling be employed a'suitable gasket may be provided between the collar 8 and the shoulder I as presently will be described. Y

VA second ring or collar I2 having a diameter less than the smallest diameter ofthe apertures 4 and 5 is provided .on the opposite end of anode 1. Collar I2 is made with a smaller diameter than collar 8 in order that the electron discharge device may be readily inserted or removed from the pole pieces. The second advantage of providing the electron discharge device with a smaller collar at one end is that this `'permits unrestrained expansion and contraction of the electron discharge device within one of its mountings. It will be noted from the drawings that inner end of brass housing I3 slides over the top of, collar l2. If water cooling be employed, a second gasket I4 is also provided at this end of the discharge device but in this case the gasket is placed around the collar rather than in front of it. As brass housing I3 is forced against gasket I4 by follower I3' the gasket expands in a radial direction and a fluid tight seal is formed thereby.

A non-magnetic spool I5 having a center aperture of the same diameter as that of aperture 3 and 4 snugly fits the conical ends of pole pieces 5 and 6. Spool I5 hasvthe dual function of provlding a suitable mounting for a magnetic modulating coil. and a flux control ring which will hereinafter be described and of providing a jacket about anode 1 which cooperates with pole .pieces 5 and 6 to form a water jacket for the elec- ,outlet conduit I1 to this space and by circulating water therethrough a convenient type water Vjacket is formed.

yThe cathode of electron discharge device 2 extends axially thereof and is a continuation of conductor I9 which forms the central conductor of a concentric transmission line I8 the outer conductor of which comprises a hollow tube 20. An exposed portion 2| of conductor I9 constitutes the radiating member of the transmitting system. This exposed portion 2| has a length determined in accordance with the radiation pattern desired. yConductor I9 is terminated for radio frequencies by a tuning disk 22u which slides on conductor I9, the electrical significance of which will hereinafter be more fully explained. Disk 22 is movedback and forth along conductor I9 until maximum output is obtained. Theoretically this places disk 22 atan odd multiple of a quarter wave length from the center of the cathode of discharge device 2. The antenna length may be held constant when tuning by means of disk 22 by proper adjustment of a slide tube 23 which nts within the outer tube 20 andwhich may be coupled mechanically to disk 22 ,by suitable insulation.l For this purpose disk 22 and tube 23 may be Vattached to non-conducting member 23. Thus by varying the position of member 23 tuning may be eiiected without varyingl the length of the antenna. Either of these members may, however, be adjustably connected tor unidirectional characteristics.

sultsare obtained when reflector 21' is placed at to member 23' to permit varying the length of the antenna upon change of frequency.

A metal collar 24 (Fig. 4) is secured tothe end of the slide tube 23 to render the radiation field Y pattern of the antenna more symmetrical. The outer iiange 25 of collar 24 has the same diameter as tuning disk 22for symmetry. An inner constrictionV 25Vis provided to reduce the radiation which would otherwise come out the end of the tube 23. Hence constriction 25 further improves the symmetry of the radiation pattern. A thin mica washer 26 which closely fits the antenna wire and is clamped between collar k24 and tube 23 serves to center and support the antenna wire. f

A small circular, plane reilector 21 is placed in front of exposed portion 2| to give the radia- The best reapproximately an odd multiple of a quarter wave j length in front of exposed portion 2| for at that point maximum energy is reected in the desired direction. Radiator 2| Yis placed at approximately the optical focus' of a large parabolic mirror 29 (such for example as a metal mirror of the 'type commonly employed Lfor airport ybeacons having a 24" diameter and a'101/2" focallength). The metal frame 28 which carries reflector 21 `is in the cathode circuit of the generator and regulation Vof the potential applied across the cathode. The complete cathode heating circuit extends from the high side of source 3U through resistor 3|; conductor 32, the cathode of discharge device 2, conductor I9, jumper wire 33, frame 28, concentric conductor 20,.binding post 34, conductor 35, to the grounded side of source 30.

Ahigh potential (for'exampie, 4000 volts) is applied to the anode of discharge device 2. The

Since'modulation of the electronic oscillations may be obtained by causing a fluctuation of the anode potential at the modulating frequency, a modulator of this type is indicated conventionally by rectangle 31. The complete anode circuit extends from the high side source 36 through conductor 38, anode modulator 31, conductor 39, pole piece 6, the anode of discharge device 2, the cathode of discharge device 2, conductor I9, and thence through the cathode circuit previously traced to groundland to the negative side of source 36.

From the foregoing description, it is apparent that high frequency oscillations are produced solely on the'cathode and in the associated cathode circuit. That is, the cathode-potential rises and falls above and below ground potential at an extremely high frequency. The anode is maintained at a nxed potential above ground 'and no variation thereof occurs. For this reason the circuit I employ may be termed a lament swing circuit. To the best of my knowledge, prior art f circuits have been confined to the see-saw type,

tion frequency or as in' asplit anode magnetron Y in which the two anode halves vary'with respect to each other atY the oscillationV frequency. The filament swing type of circuit which Il have devisedipermits the use of a massive anode, a feature 'which is necessary'if a large amount of poweris'to be dissipated. In the ..seesaW type f circuit, the anode or anodes must be keptfreladissipate power.

tively small in 'order Ynotto load the circuit with excessive capacity.' This limitation in the seesaw type circuit definitely limits their'ability to Hence, the filament swing .type

" of circuit constitutes an important improvement overV the prior art for here the major limitation onl power output of ultra high frequency waves is removed.

- l The .frequency ofoscillations generated in the I magnetron of my invention is primarily a func- 4`of the transmitter may be regulatedQ tion 'of the magnetic field intensity. Hence, it is vdesirable to provide a means for controlling the field intensity in orderthat the output frequency embodiment of my invention shown in Fig. l, I have provided a variable magnetic shunt comprisingtwo ,soft iron plates 4U'and 4|, which slide von the under surfaces of ypole pieces and 6 respectively. A control shaft 42 is provided with a Aset'of right-hand screw'threads and a set of left-hand screw threads, which threads cooperate with corresponding threads in plates 40 and 4| .in `such a manner that the platesV may be moved f closer together or farther apart, depending upon `the direction of rotation of the control shaft.

` Since the soft iron plates 40 and 4| act as a magnetic shunt path for the' main field, a simple control of the magnetic eld strength in the air gap between the pole pieces 5 and 6 is obtained. The whole equipment is mounted on a base 43.

It has been found that the power output of the `transmitter of my invention is extremely sensi- `tive to the distribution of magnetic flux lines in the YAYair gap. It will be observed that the pole pieces are shaped to concentrate the flux within thedischarge device. That,is,by reason of their receding faces, an efficient concentration of flux k density is produced fromrpole to pole through rthe-discharge device'. While it will -be understood ,that the pole pieces may have any suitable shape to effect this concentration of flux, the conical pole pieces described have been found to operate satisfactorily.

'I Vhave further found that the power output may be increased many fold, and sometimes as y .Since the oscillation'amplitude'of the transmitter. appears to be extremely'sensitive to the distribution of flux lines in the air gap, modula- 'tion of the electronic oscillations may be obn tained by superimposing a small magnetic field upon the main magnetic field, and by causing the lsmall field to vary at modulating frequency. .Suchfa small magnetic field may be obtained by Y' mounting a small coil45 in the air gap between Affpole pieces 5 andr 6 and by applying thereto an yalternating current having the frequency with `v\ ;s'1hi ch-itis desired to modulate the short wave oscillations. A source'vof such alternating cur- Hrent is',conventionallylindicated by a rectangle y @46. YThe preferred location kof flux control ring .44 and modulating coil 45 may be better seen by referring to Fig. v2 whereinI have shown an In the Y enlarged section of this portion of the transmitten v 'I'he electron discharge device 2 is illustrated in detail in Fig. 3 and includes an axial cathode 41, a long concentric cylindrical anode 1, a pair of end envelopes 48 and 49 and a cathode tensioning spring 5S. Cathode 4`| is supported between two conductors I9 and 5|. Spring 50 is connected between conductor 5| and conductor 52 and maintains cathode 41 taut at all times. If spring 50 be not a satisfactory conductor of electricity, a jumper 53 may be employed as a current carrying means between conductors 5| and 52. 'It is desirable to place the seal made between envelope 48 and conductor |9 at a voltage node on the conductor.

Anode 'I is built considerably longer than cathode 4l in order that substantially all of the electrons emitted from the cathode will eventually be collected on the anode 1. It should be noted that because the electron discharge device 2 is Vmounted with its opposite ends in axial apertures of theA pole pieces and that since a portion of the anode 'l is also located within these axial apertures, that the electrons in this region will pass rapidly to the anode for the reason that the magnetic field is lgreatly reduced Within the apertures of the pole pieces. The combined effect of the long anode and the released magnetic field at the ends prevents electron puncture trouble at the ends of the discharge device.

Where a uniform straight magnetic field, such as may be obtained by widely separating the pole pieces 5 and 6, is used for magnetron operation, it has been proposed to rotate the magnetron from 5 to 10 degrees with respect to the direction of the magnetic field in order to increase the output. I'have found that this is not generally necessary .where a slightly non-uniform magnetic field is provided. The special construction of pole pieces 5 and 6 having receding faces and provided with apertures for housing the ends of the electron discharge device produce the desired concentration of flux density in the air gap and give it the desired slightly non-uniform character and in addition provide the desirable weak field within the axial apertures for electron release to the anode. y

One of the important features of my inventionis the method used for electrical tuning. A metal disk 54 is mounted on conductor 5| to produce an approximate node of potential at that point of the conductor where the disk is located, thereby to reduce loss of energy from the corresponding end of the oscillator by reflecting this energy back into the active part of the discharge device.y The abrupt change in impedance of conductor 5| caused by the presence of disk 54 produces the desired refiection. In practice, it has been ifound that tuning disk 54 causes greatest oscillation amplitude when located at a point slightly to one side or the other of the calculated odd multiple of a quarter wave length from the centerof the cathode, depending upon the physical dimensions of the particular discharge devise used. Since it is not practicable to shift the position'of disk 54 after discharge device 2 is once constructed, it is obvious that the intensity of the magnetic field should be so adjusted that the discharge device will operate at one of the optimum output points which means that the frequency is determined by the position of disk 54 and other design factors. A frequency which will place disk 54at approximately the 1% or 5%; wave length point has given very satisfactory operation.

Disk 22 on conductor I9 functions as an electrical tuningelement in the same manner as disk 54. Provision, however, is made for sliding disk 22 along conductor I9 until maximum output is obtained for any particular oscillation frequency generated in discharge device 2. Presumably, maximum output occurs when the disk, which produces an approximate potential node on the conductor, is located at an odd multiple of a quarter wave length from the center of cathode 4l.

The operation of my transmitter is as follows: Cathode 41 is heated to the required temperature by source 39 and anode 'I is raised to the proper high potential by source 36. The intensity of the magnetic field about discharge device 2 is then adjusted by the magnetic shunt 40-4I until a wave length is obtained at which the transmitter operates with good output. As previously indicated, optirna of output occur at a number of different frequencies which are best found by trial. Tuning disk 22 has to be adjusted along conductor I 9 until maximum power output is obtained.

As a result of the combined effect of the electrostatic and electromagnetic fields, electrons leave cathode 4I and follow spiral paths to anode 'a'. The transit time of an electron depends largely upon the strength of the magnetic eld. Apparently, the electrons leaving cathode 4I, migrate in groups at a frequency depending upon their transit time. In consequence thereof a high frequency wave is produced on conductor I9 and is radiated from the exposed portion 2|. Disk reflector 21 concentrates the radiated wave on the large parabolic reflector 29. Since exposed portion 2I is at the focus of the parabolic mirror 29, a highly directional radio wave is sent out from the system.

If a modulated wave be desired, either modulator 37 or modulator 46 may be placed into operation. Application of an alternating current having a frequency of the desired modulating signal to modulating coil 45 causes a variation of the flux distribution in the air gap between pole pieces 5 and 6 at the modulating frequency. This causes an amplitude modulation of the generatedl oscillations. Variation of the magnitude of the high voltage applied to anode 'I at the modulating frequency also causes an amplitude modulation of the electronic oscillations since a variation of anode potential also varies the output of the discharge device. If desired, both modulators may be used together.

Using a transmitter built in conformity to the above description, I have obtained exceptionally good results when operating at a wave length of only 4.8 centimeters. A regular broadcast program has been transmitted over a distance of many miles by using a carrier of this wave length and the signal was received well above the noise level. I have also been able to produce oscillations of even shorter wave lengths and alsowith sucient power output for many practical applications.

A modified form of my invention is shown in Figs. 5 and 6. In this modification, a different method of cooling the magnetron is employed, a slightly modified method of electrical tuning is adopted, and provision is made for rotating the electron discharge device from 5 to 10 degrees with respect to the magnetic eld. Referring to Fig. 6, it will be seen that an electron discharge device having an anode 'I is supported by a pair of metal jaws 60 and 6I. These metal jaws may be placed between the pole pieces and at right angles thereto to'support the discharge device within the apertures of the pole pieces. Jaws 6U and 6I form ay convenient method of support which readily permits an angular shift of the discharge device with respect to the magnetic field, that is, to a position out of parallelism with the axis of the magnetic field. These jaws also provide an extremely simple method of conducting heat away from anode 'I. An aperture 62 in jaw 60 and an aperture 63 in` jaw 9| provides a passage for the cooling fluid received through inlet pipe 64 and discharged through outlet pipe 65.r A short flexible U-shaped pipe 66 connects aperture 62 with aperture 63.

Referring now to Fig. 5, it will be seen that the cooling tubes 54 and 6G are shown herein arranged in a plane between the pole pieces and at right angles thereto, which plane includes the jaws 6i? and 5I.

This figure also shows a pair of tuning members 8l Yand 6l', which are used in the place of the single tuning disk 54 previously described. Tuning member Si may be located at the same place that tuning disk 54 of Fig. 1 is located or it may be placed nearer'the cathode il and within the metal anode 'I. Tuning disk 61 is shown as being exterior to envelope 49. Tuning members @l and G'I' are so placed as to reflect energy back in the direction of the transmission line and thereby reduce back-end losses. Any stray energy which gets by tuning member B'I is substantially stopped by tuning member 6l. A shield 98 extends from tuning disk 6l' back over a portion of anode 'I further to prevent loss of energy from this portion of the apparatus. In order to permit rotation of the discharge device with respect to the magnetic field, a slightly diiferent formof pole piece construction is necessary. Pole pieces E9 and 'I9 are provided with apertures 'II and 'l2 which preferably are of conical shape in the place of the form tting apertures of pole pieces 5 and 6 of Fig. l. These conical apertures 'II and 'I2 permit an angular rotation of 5 to 10 degrees of the magnetron with respect to the magnetic eld.

Where the magnetic eld is substantially uniform over the active portion of the discharge device, the anode should extend beyond the eifective electron emitting portion of the cathode at each end by at least the radius of the anode times the cotangent of the angle of tip, that is, the angle between the axis of the discharge device and that of the magnetic eld. As previously pointed out, the provision of an anode which is substantially longer than the cathode entirely eliminates puncture trouble in the glass envelope 4a and 49 at the ends of themagnetron by assuring that substantially all of the electrons are collected on the anode.

A further modification of my invention is shown in Fig. 7. In this modification the required magnetic field about discharge device 2' is produced by a pair of large electromagnets 'I3 and '14. Two conical pole pieces 'I5 and 'IS house discharge device 2 in a manner similar to pole pieces 5 and 6 of Fig. '1. rI'wol sleeves 'I'I and 'I8 may be used to electrically insulate magnet coils 'I3 and 'I4 from pole pieces 'I5 and l. Inlet passage '59 and outlet passage 80 for the fluid cooling medium are formed in the pole pieces in a somewhat different manner and connect with the space about the anode of the discharge de- While I have Vdisclosed in pipes 8| and' '82fconnect' passages 19 and 80`to the fluid circulating system Y(not shown) return magnetic path is provided :by end f'piatestaV and plates a4.V y

Fig. 1 a form of friet, I wish to point out that the permanent magnetfvhas decided advantages with respect to the I ,constancy of frequencywhich may be produced.

Since the kfrequencyofrioscillation produced in my v'invention isl dependent upon the intensity of the magnetic field, it is important that this field be ,.heldf, constant. It' has `been found that this canY best be accomplished byl use of a permanent lfmagnet, andffu'rther that by proper choice of Yobje'itionable dimensions. "comprise, for example, 63% iron, 20%v nickel," 112% aluminum, and 5% cobalt.

materials a v'permanent magnet can be con-v structed for usein myinvention which is not of The magnet may I believe that l `Ifhave,been'the first to provide a practical short wave oscillation generator ofthe magnetron type Airrvvhicln the advantage of permanent magnetism isY taken Vto produce the main magnetic field 'y therebyto produce oscillations having frequency `of improved constancy and extremely short wave length. Y j ,I-Ierein, where I have'used the term odd vmul- ,ftiple' of. a quarter wave length, it vWillof course be understood vthatjI include theY multiple one. vrWhile I have shown particular embodiments "cof my invention, it `willof course be understood Y ,that vI do not wish'to be limited thereto since many modifications may be madeboth in thek lcircuit'larrangement and in the instrumentalities employed, [and that I therefore contemplate by fthe'fappended claims to cover all such modifications as fall within'the true spirit and scopeV of 1j '.'my invention;

f Thetransmitter and sub-combinations thereof,

' hereinabove described, are claimed in application,

V'Serial No.v 215,794, filed June 25, 1938, which is Yadivision Vof my present application.

"i fLettersPatent of the United States is:

vWhat I claim as new and desire toA secure.k by

1.In combination, 1a.,.magn'et, a pair ofpole pieces, and an electron discharge device having an'ariode and 'a' cathode, a substantial portion of Y said'-"ar1ode 'being housedwithin said pole pieces ,andthe activel portion, of said cathode beingv 4located between said pole pieces. .2.f`2g1n combination, a magnet, a pair of pole 55 pieces, 'and an electron, discharge device having .an anode and a cathode, a. substantial portion of said yanode being housed within said pole `pieces andthe Aactiv portion of said cathode wbe'ing located between said pole pieces, the opco,

posed faces of said pole pieces receding from each j fother rat increasing distances from said discharge l.devicer thereby to concentrate the 'flux between o .y said pole pieces within said discharge device.

3. In combination, a magnet, apair of pole lpieces secured thereto having axial apertures l therein and an electron discharge device substanvtially housed within said apertures. f l 4, In combination, a pair of opposed magnetic Apole pieces, apertures in sald'pole pieces, and a discharge device mounted within said apertures.

5. In combination, a pair of opposed magnetic 1 polepieces, aperturesin said pole pieces, a. .dis-

f charge device-mounted within said apertures, and 75 said pole pieces being so shaped as to produce a 2,145,735 ,l kvicefas maybe seen from the gure. Suitable concentration ffflux within said discharge device.

6. In combination, a pair of opposed magnetic pole pieces, apertures in said pole pieces in alignment with each other, a discharge device arranged axially within said apertures, said pole pieces being so shaped as to produce a concentration of flux within said discharge device and substantially parallel with the axis thereof.

'7. In combination,` a pair of magnetic pole pieces having faces with portions in close proximity to each other and portions receding therefrom, apertures in said first portions and an electron discharge device mounted within said apertures and extending between said pole faces whereby the magnetic ux between said pole pieces is concentrated within said discharge device.

8. In combination, a pair of magnetic pole pieces having opposed conical faces, apertures in said pole pieces and an electron discharge device mounted within said apertures and extending between said pole pieces, whereby the magnetic iiux 'between said` pole pieces is concentrated within vsufficiently longerthan said cathode that electrons leaving said cathode and traveling at a small acute angle relative thereto are collected von said anode.

'10. In combination with an electron discharge device, heat conducting jaws supporting said discharge device and means for conducting heat laway from said jaws.

11. In combination, an electron discharge device having a cathode, an anode enclosing said cathode, and a magnet having opposed pole pieces arranged to produce a magnetic iield parallel with said cathode and within said anode, the opposite ends of said anode being housed within the respective pole pieces, and a winding about said anode between said pole pieces.

12. In combination, an electron discharge device having a cathode, an anode enclosing said cathode, and a magnet having opposed pole pieces vvice having a cathode, an anode enclosing said cathode, and a magnet having opposed pole pieces arranged to produce a field parallel with said `cathode and within said anode, the opposite ends of said anode being housed within the respective pole pieces, and means to change the flux distribution within said anode and between said pole pieces.

14. In combination, an electron discharge device having a cathode, an anode concentric with said cathode, and means to produce a magnetic fieldV within said anode and at an angle to said cathode, said anode extending beyond each end of said cathode by a distance equal to at least the f product of theradius of said anode and the c0- magnetic field within said anode of such intensity that at least a portion of the electrons leaving the cathode travel at an acute angle relative thereto, said anode extending beyond either end of said cathode to such an `Vextent that substantially all of the electrons emitted by said cathode .are collected on said anode.

16. The combination, in an electron discharge device adapted for use in a short wave oscillation generator, of an `evacuated vessel comprising a cathode, an anode arranged about said cathode, said cathode being connected to conductors extending through said vessel at different points, `and a conducting member connected conductively to one of said conductors at a predetermined distance from said cathode, said member having sucient dimensions to prevent oscillation of that part of said conductor opposite said member from said cathode.

, 17. The combination, in an electron discharge device adapted for use in a short wave oscillation generator, of an evacuated vessel comprising -a cylindrical anode, a cathode extendingk coaxially of said anode, cathode circuit conductors extending through the wall of said vessel at opposite ends of said vessel, and a large conducting body conductively connected to one of said conductors.

18. The combination, lis an electron discharge apparatus, of a cylindrical anode, opposed magnetic pole pieces at opposite ends thereof arranged to produce a strong magnetic field within said anode, a cathode arranged coaxial with said anode, said anode being at ground potential at the frequency at which said device operates, and said cathode being free to oscillate at said frequency.

19. The combination, in an electron discharge apparatus, of a cylindrical anode, opposedmagnetic pole pieces at opposite ends thereof arranged to produce a strong magnetic iield vwithin said anode, a cathode arranged coaxial with said anode, said anode beingat ground potential at the frequency at which said device operates, and said cathode being free to oscillate at' said frequency, conductors extending from opposite ends of saidcathode, and a largeconductive body conductively mounted on one of said conductors to prevent oscillation of that portion of said conductor opposite said cathode at said frequency.

20. In combination with an electron discharge device having a cylindrical anode, a, cathode coaxial therewith,.and heat conducting jaws supporting said anode in a magnetic field extending longitudinally withiny said cylinder, and means to cool said jaws.

2l. The combination, in anelectron discharge apparatus, of a continuous conductor extending through a cylindrical housing, a portion of said housing comprising an anode, said portion being spaced within and between the pole pieces of a magnet whereby a strong magnetic field is produced within said anode, a portionof said conductor within said Vanode lbeing adapted to act as a cathode, said conductor being free to oscillate at short wave length while said anode is at ground potential at said wave length. t

22. The combination, in an electron discharge apparatus, of a continuous conductor extending through a cylindrical housing, a. portion of said housing comprising an anode, said portion being spaced within and between the pole pieces of a magnet whereby a strong magnetic eld is produced within said anode, a portion of said conductor within said anode being vadapted to act as a cathode, said conductor being free to oscillate at short wave length While said anode is at ground potential at said Wave length, said conductor having an exposed portion extending beyond one end of said housing, and means to coniine said oscillations to y said conductor.

23. In combination, a magnet, a pair of pole pieces secured to said magnet, an electron discharge device having an anode and a cathode, a substantial portion of said anode being housed within said pole pieces and the active portion of said Acathode being located between said pole pieces, `and means for changing the normal ux distribution lin ythe air gap between said pole pieces. A t

24. In combination, a magnet, a pair of conical pole pieces secured to said magnet, ran electron discharge device in .the magnetic field produced byfsaid magnet, and a magnetic flux control ring located between said pole pieces.V

25. In combination, an electron discharge de vice, a permanent magnet for producing a strong magnetic field within said dischargev device and for determining the frequency of oscillations in said device in accordance with the intensity of `said magnetic field, and an adjustable magnetic shunt for varying the magnetic field intensity` within said discharge device.

c 26. In combination, means for producing a magnetic eld, an velectron dischargeV device having a cathode and a concentric cylindrical anode, and means to cause rotation of said device with respect to said magnetic eld `such that the longitudinal axis of said device forms an acute angle with the line of direction of said eld, said anode extending beyond each end of said cathode a distance equal at least to the product of the radius of said anode andthe cotangent of said angle.

c 27. In an electron discharge device, the combination including a linear cathode and an anode concentric therewith, said anode being suiciently .longer than said cathode to prevent electrons which leave said cathode and travel at a small acute angle relative thereto from leaving said anode at either end thereof.

CHESTER W. RICE. 

